1. Field of the Invention
The present invention relates to an electromagnetic relay.
2. Description of the Related Art
Electromagnetic relays are devices having a main contact part that breaks or allows an electric current flow between contacts, which may be opened/closed by an electromagnetic force. Because the contacts of the electromagnetic relay are opened/closed by an electromagnetic force, arcing may occur between the contacts when the contacts are opened; namely, when the electric current flow is broken. When arcing occurs, the contacts may be overheated and damaged. In some cases, the contacts may weld together as a result.
In consideration of the highly reliable breakage performance demanded in electromagnetic relays used in a high-voltage DC (direct current) circuit of an electric vehicle or a large DC system, for example, measures are desired for effectively extinguishing arcing that occurs between contacts to improve breakage performance of the electromagnetic relays and improve durability of the contacts.
Also, a surge voltage is generated when the contacts open and close in electromagnetic relays used in a DC high voltage current circuit. Accordingly, high insulation resistance (dielectric withstanding voltage) is demanded between parts such as contacts, coils and yokes of the electromagnetic relays. To increase the insulation resistance (dielectric withstanding voltage), suitable insulation distances need to be secured between the parts.
Thus, high arc extinguishing performance and high insulation between relay parts are desired characteristics in electromagnetic relays.
In this respect, for example, Japanese Laid-Open Patent Publication No. 2011-154818 (Patent Document 1), Japanese Laid-Open Patent Publication No. 2007-214034 (Patent Document 2), and Japanese Laid-Open Patent Publication No. 2011-228087 (Patent Document 3) disclose electromagnetic relays that are configured to improve arc extinguishing performance by arranging permanent magnets near contacts.
Japanese Laid-Open Patent Publication No. 2001-118451 (Patent Document 4) discloses a contact unit having a yoke arranged at a permanent magnet, which is arranged near a contact.
Japanese Laid-Open Patent Publication No. 09-097550 (Patent Document 5) discloses an electromagnetic relay that has a body block made up of a base having at least one set of terminals of a contact mechanism insert-molded therein and an insulating cover having a tunnel-like insulating wall.
Japanese Laid-Open Patent Publication No. 2009-164147 (Patent Document 6) discloses an electromagnetic relay that is configured to secure a predetermined insulation distance between an electromagnetic unit and a contact part, and increase an electromagnetic attraction force without enlarging an outer dimension of the relay.
Japanese Laid-Open Patent Publication No. 2005-093118 (Patent Document 7) discloses an electromagnetic relay that is configured to secure a required insulation interval between adjacent relay structures by providing a surrounding wall that surrounds the adjacent relay structures in a bursiform shape and a partitioning wall interposed between the relay structures.
Although the electromagnetic relays disclosed in Patent Documents 1-4 are able to improve the arc extinguishing performance by including permanent magnets, the electromagnetic strength of the permanent magnets may be inadequate in a case where a large amount of current is flown.
Also, with respect to electromagnetic relays that are arranged in a control panel or a similar device, device miniaturization is desired for purposes of reducing the device footprint. However, the device may have to be enlarged, when measures are implemented to enhance the arc extinguishing performance or insulation of electromagnetic relays, for example.
Also, in the electromagnetic relays disclosed in Patent Documents 5-7, adequate insulation may not be secured in a case where a high voltage is applied, for example.